[llvm] 290a111 - [docs] Add a brief description of using -fveclib to enable some math library vectorizations (#119215)

[via llvm-commits]

Author: Simon Pilgrim
Date: 2024-12-09T15:06:23Z
New Revision: 290a111792577810bfd1a858f230260489cf90cf

URL: https://github.com/llvm/llvm-project/commit/290a111792577810bfd1a858f230260489cf90cf
DIFF: https://github.com/llvm/llvm-project/commit/290a111792577810bfd1a858f230260489cf90cf.diff

LOG: [docs] Add a brief description of using -fveclib to enable some math library vectorizations (#119215)

Fixes #62283

Added: 
    

Modified: 
    llvm/docs/Vectorizers.rst

Removed: 
    


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diff  --git a/llvm/docs/Vectorizers.rst b/llvm/docs/Vectorizers.rst
index c2beb1669c4e3b..a4462e53edda09 100644
--- a/llvm/docs/Vectorizers.rst
+++ b/llvm/docs/Vectorizers.rst
@@ -345,6 +345,16 @@ instruction is available.
       f[i] = floorf(f[i]);
   }
 
+Many of these math functions are only vectorizable if the file has been built
+with a specified target vector library that provides a vector implemention
+of that math function. Using clang, this is handled by the "-fveclib" command
+line option with one of the following vector libraries:
+"accelerate,libmvec,massv,svml,sleef,darwin_libsystem_m,armpl,amdlibm"
+
+.. code-block:: console
+
+   $ clang ... -fno-math-errno -fveclib=libmvec file.c
+
 Partial unrolling during vectorization
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^